Decomposable extended-reach frac plug, decomposable slip, and methods of using same

ABSTRACT

A plug for hydraulic fractionation can have a first driver; a first pressure arm rotatably connected to the first driver; a second driver; a second pressure arm rotatably connected to the second driver; and a first slip rotatably connected to the first pressure arm and rotatably connected to the second pressure arm. The frac plug can also have a third driver; a third pressure arm rotatably connected to the third driver; a fourth driver; a fourth pressure arm rotatably connected to the fourth driver; and a second slip rotatably connected to the third pressure arm and rotatably connected to the fourth pressure arm. Preferably at least a portion of the frac plug is a material formulated to decompose in one to twenty-four hours under typical wellbore conditions. Moreover, a decomposable slip is provided for use with any frac plug known to one of ordinary skill.

PRIORITY CLAIM

The present application claims priority to U.S. provisional application Ser. No. 62/007,698, filed on Jun. 4, 2014, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates generally to devices for hydraulic fracturing (“fracking”). More specifically, the present disclosure is directed to frac plugs and slips that can be at least partially decomposable and/or can use pressure arms to radially extend the slip from the plug.

The fracking process begins by drilling a wellbore into the earth to reach hydrocarbons trapped in shale formations. A perforating gun or other device is then used to create small holes in the wall of the wellbore. Fluid is pumped into the wellbore to form a pressure greater than the fracture gradient of the surrounding formation. This pressure creates large fractures in the shale formation, thus providing access to the oil or natural gas trapped within the formation.

To fracture a wellbore, the wellbore is divided into separate zones so that the necessary pressure can be established in the zones. The bottom-most zone is typically fractured first, using the above-described process. The driller next inserts a frac plug at the top/uphole side of the fracked zone. A frac plug can stop fluid flow in one or both directions. The frac plug isolates the previously-fracked lower zone from the next zone uphole in the wellbore, thus ensuring that the hydraulic pressure is applied to the unfracked zone and not the previously-fracked lower zone. This process of plugging and fracking continues until the entire production area of the wellbore has been fracked and plugged. The process can involve a dozen or more frac plugs per wellbore.

To position the frac plug within the wellbore, components of a frac plug (known as the “slips” and the “seal”) expand to engage wellbore sidewalls and create a barrier separating upper and lower regions of the wellbore. The process of expanding the plug is called “setting,” and involves pulling upward on the body of the plug with a setting tool while pushing downward on the slips and the seal with a setting sleeve. This axial compression causes the slips to move outward along a conical element, thus radially expanding the slips into engagement with the wellbore sidewalls to maintain the position of the plug in the wellbore. The setting pressure also causes the malleable seal, usually made from rubber, to expand outward against the well casing to prevent liquid or gas from passing around the plug.

There are several problems with known frac plugs. First, the design of the frac plug generally limits its use to wellbores of a diameter that corresponds to the diameter of the expanded slip. For example, if a frac plug is used in a wellbore that is so wide that the expanded slip does not reach the wall of the wellbore, such a frac plug cannot be used in the wellbore; the desired position of the frac plug cannot be maintained in such a wellbore.

A second problem arises from the need to remove the frac plugs to allow oil and gas to move toward the surface. Typically a tool is used to drill or mill through the plug. After the tool cuts through the slips, the remaining head member is free to move through the well casing and is difficult, if not impossible, to drill by itself. As a result, the tool pushes the head down the well casing until stopped by the next plug. The lower plug holds the upper head member in place so that the drilling process can continue. The time, equipment, labor and energy expended in this process of removing the plugs are costly and thus delay hydrocarbon extraction and decrease profitability.

SUMMARY

In a general embodiment, the present disclosure provides a frac plug comprising a first driver; a first pressure arm rotatably connected to the first driver; a second driver; a second pressure arm rotatably connected to the second driver; and a first slip rotatably connected to the first pressure arm and rotatably connected to the second pressure arm.

In an embodiment, the frac plug further comprises a third driver; a third pressure arm rotatably connected to the third driver; a fourth driver; a fourth pressure arm rotatably connected to the fourth driver; and a second slip rotatably connected to the third pressure arm and rotatably connected to the fourth pressure arm.

In an embodiment, the frac plug comprises at least one seal, the second driver is fixedly connected to and/or integral with a first seal back-up that has a bevel complementary to a first portion of the at least one seal, and the third driver is fixedly connected to and/or integral with a second seal back-up that has a bevel complementary to a second portion of the at least one seal that is at an opposite end of the at least one seal from the first portion.

In an embodiment, the first driver comprises an axial slot into which a portion of the first pressure arm inserts.

In an embodiment, the first driver comprises a socket in which a pin is positioned to extend through the portion of the first pressure arm inserted into the axial slot.

In an embodiment, the first pressure arm, the first slip, and the second pressure arm each comprise an aperture through which a pin is inserted to connect the first pressure arm, the first slip, and the second pressure arm to each other.

In another general embodiment, the present disclosure provides a fractionation plug comprising a material formulated to decompose in one to twenty-four hours under typical wellbore conditions.

In an embodiment, the fractionation plug has an outside diameter configured such that the frac plug can be installed in casing or tubing with an inside diameter from 2 inches to 4 inches, such as an inside diameter of 2.259 inches as a non-limiting example.

In an embodiment, the fractionation plug is configured to be expanded to set in casing or tubing with an inside diameter from 2 inches to 5.5 inches, such as an inside diameter of 5.5 inches as a non-limiting example.

In an embodiment, the fractionation plug is designed to be installed and maintain isolation of hydrocarbon bearing zones for a predetermined period of time.

In an embodiment, the fractionation plug is configured to begin to decompose and release from a wellbore in which the fractionation plug is positioned, when subjected to a chemical selected from the group consisting of water, acid, alkaline and non-alkaline, such as brine water as a non-limiting example.

In an embodiment, the fractionation plug is the fractionation plug is configured to undergo decomposition catalyzed by a temperature of a wellbore and/or a fluid in a wellbore.

In an embodiment, the fractionation plug is configured to be installed on at least one of e-line, wireline or coil tubing.

In an embodiment, the fractionation plug is configured to be drilled out with conventional tubing or coiled tubing.

In another general embodiment, the present disclosure provides a slip configured to be mounted on a mandrel of a fractionation plug. The slip comprises: a body comprising a decomposable material; and a coating at least partially covering the body, the coating comprising a metal material.

In an embodiment, the metal material is formulated to at least partially decompose within one to twenty-four hours after being exposed to a temperature between 150 and 380° F., and the slip is configured such that the at least partial decomposition of the metal material exposes at least a portion of the body that was previously covered by the coating.

In an embodiment, the slip comprises teeth comprising exterior surfaces comprising at least a portion of the coating.

In an embodiment, the teeth form an outer side of the slip, and the coating completely covers the body on at least the outer side of the slip.

In an embodiment, the decomposable material of the body comprises a decomposable resin.

In an embodiment, the decomposable material of the body comprises a resin-fiber mixture comprising metallic or non-metallic particulates, such as magnesium particulates as a non-limiting example.

An advantage of the present disclosure is to provide an improved frac plug.

Another advantage of the present disclosure is to provide an improved frac plug slip.

Still another advantage of the present disclosure is to provide a frac plug and/or a slip that can decompose within one to twenty-four hours under typical wellbore conditions.

Yet another advantage of the present disclosure is to provide a decomposable frac plug designed to isolate zones in a wellbore until a chemical, such as an acid or brine water mixture, is applied to initiate decomposition and release of the plug from the walls of the wellbore.

Another advantage of the present disclosure is to provide a decomposable frac plug that uses the temperature of the wellbore as a catalyst to begin decomposition.

Still another advantage of the present disclosure is to provide an extended reach frac plug with an outside diameter small enough to install in casing or tubing with a small inside diameter, for example an inside diameter of about 2.259″.

Yet another advantage of the present disclosure is to provide an extended reach frac plug that can be installed through tubing, for example 2⅞″ or 3½″ tubing, and upon reaching setting depth being capable of expanding to set in a casing with a wider diameter, for example 5½″ casing.

Another advantage of the present disclosure is to provide an extended reach frac plug capable of being installed and maintaining isolation of zones for a predetermined period of time.

Still another advantage of the present disclosure is to provide an extended reach decomposable frac plug capable of being installed on e-line, wireline, or coil tubing.

Yet another advantage of the present disclosure is to provide an extended reach decomposable frac plug capable of being drilled out with conventional tubing or coiled tubing.

Another advantage of the present disclosure is to provide an extended reach frac plug capable of being installed in wellbores with significantly different diameters.

Additional features and advantages are described herein and will be apparent from the following Detailed Description and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a side plan view of an embodiment of a frac plug provided by the present disclosure, in the pre-setting configuration.

FIG. 2 shows a side plan view of an embodiment of a frac plug provided by the present disclosure, in a set configuration.

FIG. 3A shows a side plan view of a slip in an embodiment of a frac plug provided by the present disclosure.

FIG. 3B shows an above plan view of a slip in an embodiment of a frac plug provided by the present disclosure.

FIG. 4A shows a side plan view of a pressure arm in an embodiment of a frac plug provided by the present disclosure.

FIG. 4B shows an above plan view of a pressure arm in an embodiment of a frac plug provided by the present disclosure.

FIG. 5A shows a cross-section view of a driver in an embodiment of a frac plug provided by the present disclosure.

FIG. 5B shows a side plan view of a driver in an embodiment of a frac plug provided by the present disclosure.

FIG. 6A shows a side plan view of a pin in an embodiment of a frac plug provided by the present disclosure.

FIG. 6B shows an above plan view of a pin in an embodiment of a frac plug provided by the present disclosure.

FIG. 7A shows a side cross-section view of a first seal back-up integral with the second driver in an embodiment of a frac plug provided by the present disclosure.

FIG. 7B shows a side cross-section view of a second seal back-up integral with the third driver in an embodiment of a frac plug provided by the present disclosure.

FIG. 8A shows an above plan view of an embodiment of a decomposable slip provided by the present disclosure, in a non-expanded configuration.

FIG. 8B shows a side cross-section view of a segment of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 8C shows a side perspective view of a body of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 8D shows a side perspective view of a coating of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 8E shows a side plan view of a coating of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 8F shows an above plan view of the embodiment of a decomposable slip shown in FIG. 8A, in an expanded configuration.

FIG. 9A shows a side perspective view of a frac plug in which an embodiment of a decomposable slip provided by the present disclosure can be used.

FIG. 9B shows a side cross-section view of the frac plug of FIG. 9A along line X-X.

FIG. 10A shows a side cross-section view of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 10B shows an above plan view of the embodiment of a decomposable slip shown in FIG. 10A.

FIG. 10C shows an above plan view of a segment of the embodiment of a decomposable slip shown in FIGS. 10A and 10B.

FIG. 10D shows a side perspective view of the embodiment of a decomposable slip shown in FIGS. 10A-10C.

FIG. 11A shows a side cross-section view of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 11B shows an above plan view of the embodiment of a decomposable slip shown in FIG. 11A.

FIG. 11C shows an above plan view of a segment of the embodiment of a decomposable slip shown in FIGS. 11A and 11B.

FIG. 11D shows a side perspective view of the embodiment of a decomposable slip shown in FIGS. 11A-11C.

FIG. 12A shows a side cross-section view of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 12B shows an above plan view of the embodiment of a decomposable slip shown in FIG. 12A.

FIG. 12C shows an above plan view of a segment of the embodiment of a decomposable slip shown in FIGS. 11A and 11B.

FIG. 12D shows a side perspective view of the embodiment of a decomposable slip shown in FIGS. 11A-11C.

FIG. 13A shows a side cross-section view of an embodiment of a decomposable slip provided by the present disclosure.

FIG. 13B shows an above plan view of the embodiment of a decomposable slip shown in FIG. 13A.

FIG. 13C shows an above plan view of a segment of the embodiment of a decomposable slip shown in FIGS. 13A and 13B.

FIG. 13D shows a side perspective view of the embodiment of a decomposable slip shown in FIGS. 13A-13C.

FIG. 14A is a side cross-section of an embodiment of a mandrel provided by the present disclosure.

FIG. 14B is a side cross-section of the embodiment of a mandrel shown in FIG. 14A.

FIG. 15A is a side cross-section of an embodiment of a load ring provided by the present disclosure.

FIG. 15B is a side cross-section of the embodiment of a load ring shown in FIG. 15A.

FIG. 16A is a side cross-section of an embodiment of a combination of a mandrel, a load ring and a decomposable slip provided by the present disclosure.

FIG. 16B is a side cross-section of the embodiment of a combination of a mandrel, a load ring and a decomposable slip shown in FIG. 16A.

DETAILED DESCRIPTION

As used in this disclosure and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. The words “comprise,” “comprises” and “comprising” are to be interpreted inclusively rather than exclusively. Likewise, the terms “include,” “including” and “or” should all be construed to be inclusive, unless such a construction is clearly prohibited from the context. However, the devices disclosed herein may lack any element that is not specifically disclosed. Thus, a disclosure of an embodiment using the term “comprising” includes a disclosure of embodiments “consisting essentially of” and “consisting of” the components identified.

An embodiment of a frac plug 10 provided by the present disclosure is shown in FIGS. 1 and 2. FIG. 1 shows the frac plug 10 before the frac plug 10 is set in a wellbore. FIG. 2 shows the frac plug 10 after the frac plug 10 is set in a wellbore.

The frac plug 10 can comprise a mandrel 20 to which a nose cone 21 can be fixedly connected at one end and a crown 24 can be fixedly connected at the opposite end. For example, the nose cone 21 can be connected to or formed on a lower end of the mandrel 20, and the crown 24 can be formed on or connected to an upper end of the mandrel 20. In an embodiment, the nose cone 21 is connected to the mandrel 20 by a brass pin.

The nose cone 21 can comprise a slot 22 that can extend through the nose cone 21 in a direction parallel to the mandrel 20. In an embodiment, an end of the nose cone 21 can be tapered, for example at about thirty-five degrees relative to the axis of the frac plug 10. The crown 24 can comprise one or more grooves 25 with a shape that is complementary to the nose cone 21. The tapered end of the nose cone 21 of the frac plug 10 can insert into the one or more grooves 25 of a lower frac plug (not shown) during drill-out operations. Accordingly, the nose cone 21 of the frac plug 10 can engage the crown 24 of a lower frac plug to prevent rotation of the frac plug 10 during drill-out.

The frac plug 10 can comprise a first driver 41 which may be adjacent to the nose cone 21. The frac plug 10 can further comprise a second driver 42 on an opposite side of the first driver 41 relative to the nose cone 21. The frac plug 10 can comprise a third driver 43 and can further comprise a fourth driver 44 that is adjacent to the crown 24. The third driver 43 can be positioned on an opposite side of the fourth driver 44 relative to the crown 24. The first, second, third and fourth drivers 41-44 can be cylindrical rings that can slide on the mandrel 20 and can rotate on the mandrel 20.

Each of the first, second, third and fourth drivers 41-44 preferably has an inner diameter that is substantially the same as the outer diameter of the mandrel 20. In an embodiment, this diameter can be about 1.25 inches. The first, second, third and fourth drivers 41-44 preferably have an outer diameter that is substantially the same relative to each other. In an embodiment, this diameter can be about 2.625 inches. In an embodiment, the non-tapered portion of the nose cone 21 has an outer diameter that is substantially the same as that of the first, second, third and fourth drivers 41-44. These dimensions are non-limiting and illustrative only, and one of ordinary skill will recognize that the specific dimensions implemented in the frac plug 10 can be adjusted based on the parameters of the operation, such as wellbore size, and proportionality to other components of the frac plug 10.

The frac plug 10 can comprise one or more slips disposed about the mandrel 20 between the crown 21 and the nose cone 22. For example, the frac plug 10 can comprise first slips 31 and a second slips 32. Each of the first and second slips 31,32 can be moveably mounted on the frac plug 10. The first slips 31 and/or the second slips 32 can be used to set the frac plug 10 within a wellbore. Preferably, the frac plug 10 comprises four of the first slips 31, each positioned at ninety degrees relative to each other at the same axial distance along the frac plug 10, and the frac plug 10 comprises four of the second slips 32, each positioned at ninety degrees relative to each other at the same axial distance along the frac plug 10. However, the frac plug 10 can comprise any number of first slips 31 and any number of second slips 32, and the first and second slips 31,32 can be at any position relative to each other.

In an embodiment, one or more of the first and second slips 31,32 comprise a metal, such as brass, through which a tool is drilled during a drill-out operation to remove the first and second slips 31,32 from the wellbore. In an embodiment, one or more of the first and second slips 31,32 comprise a decomposable material so that a drill-out operation is not necessary and/or is minimized, as discussed in further detail later in this application.

FIGS. 3A and 3B generally illustrate a slip 100 that can be used as one or more of the first and second slips 31,32. In a preferred embodiment, each of the first and second slips 31,32 are one of the slip 100. The slip 100 can comprise one or more sets of ridges or teeth 102.

To set the frac plug 10 in the wellbore, the first and second slips 31,32 can be moved outward relative to the mandrel 20 to engage the one or more sets of ridges or teeth 102 with an inner surface of a casing or production tubing. Preferably the one or more sets of ridges or teeth 102 of the first slips 31 are sloped toward the nose cone 21 such that they face the nose cone 21 and the one or more sets of ridges or teeth 102 of the second slips 32 are sloped toward the crown 24 such that they face the crown 24.

The slip 100 can comprise a first leg 106 and a second leg 108 that extend from the one or more sets of ridges or teeth 102. The slip 100 can comprise a channel 104 that extends through the first leg 106 and/or the second leg 108. The channel 104 can be used to connect the slip 100 to the first and second drivers 41,42 or to the third and fourth drivers 43,44, as discussed in more detail hereafter.

Referring again to FIGS. 1 and 2, the first slip 31 can be rotatably connected to a first pressure arm 35 and a second pressure arm 36. The first pressure arm 35 can be rotatably connected to the first driver 41, and the second pressure arm 36 can be rotatably connected to the second driver 42. Preferably one end of the first pressure arm 35 is rotatably connected to the corresponding first slip 31 by a pin, and an opposite end of the first pressure arm 35 is rotatably connected to the first driver 41 by another pin. Preferably one end of the second pressure arm 36 is rotatably connected to the corresponding first slip 31 by still another pin, and an opposite end of the second pressure arm 36 is connected to the second driver 42 by yet another pin.

Each of the second slips 32 can be rotatably connected to a third pressure arm 37 and a fourth pressure arm 38. The third pressure arm 37 can be rotatably connected to the third driver 43, and the fourth pressure arm 38 can be rotatably connected to the fourth driver 44. Preferably one end of the third pressure arm 37 is rotatably connected to the corresponding second slip 32 by a pin, and an opposite end of the third pressure arm 37 is rotatably connected to the third driver 43 by another pin. Preferably one end of the fourth pressure arm 38 is rotatably connected to the corresponding second slip 32 by still another pin, and an opposite end of the fourth pressure arm 38 is connected to the fourth driver 44 by yet another pin.

FIGS. 4A and 4B generally illustrate a pressure arm 110 that can be used as one or more of the first, second, third and fourth pressure arms 35-38. In a preferred embodiment, each of the first, second, third and fourth pressure arms 35-38 are one of the pressure arm 110. The pressure arm 110 can comprise a first aperture 111 by which the pressure arm 110 can be connected to the slip 100. The portion of the pressure arm 110 comprising the first aperture 111 can insert between the first leg 106 and the second leg 108 of the slip 100 to align the first aperture 111 with the channel 104 through the slip 100. A pin can insert through the first aperture 111 of the pressure arm 110 and through the channel 104 of the slip 100 to rotatably connect the slip 100 to the pressure arm 110.

The pin through the channel 104 of the slip 100 can connect the slip 100 to two pressure arms 110. For example, the first slip 31 may have the form of the slip 100, and the pin therein can extend through the channel 104 of the first slip 31, the first aperture 112 of the first pressure arm 35, and the first aperture 111 of the second pressure arm 36. Similarly, the second slip 32 may have the form of the slip 100, and the pin therein can extend through the channel 104 of the second slip 32, the first aperture 111 of the third pressure arm 37, and the first aperture 111 of the fourth pressure arm 38.

The pressure arm 110 can comprise a second aperture 112 by which the pressure arm 110 can be connected to one of the first, second, third and fourth drivers 41-44. For example, as shown in FIG. 5A which depicts a cross-section of a driver 150 (one of the first, second, third and fourth drivers 41-44), a pin 120 can insert through the second aperture 112 of the pressure arm 110 into a socket in the corresponding driver 150. As a result, the pressure arm 110 can be rotatably connected to the corresponding driver 150. As shown in FIG. 5B which depicts a side plan view of the driver 150, the pin 120 can insert into the driver 150 through a first hole 151 and/or a second hole 152 in the driver 150 in order to insert through the second aperture 112 of the pressure arm 110.

As shown in FIG. 5B, the pressure arm 110 can insert into the corresponding driver 150 using an axial slot 153 in the driver. The axial slot 153 can extend into the driver 150 so that the second aperture 112 of the pressure arm 110 can align with the first and second holes 151,152 of the corresponding driver 150.

As shown in FIGS. 6A and 6B, the pin 120 can be a cylindrical pin, but the pressure arm 110 can be rotatably connected to the corresponding driver 150 using any means known to one of ordinary skill. The pin that connects the pressure arm 110 to the slip 100 can be the same as or similar to the pin 120 that connects the pressure arm 110 to the corresponding driver 150, but the pressure arm 110 can be rotatably connected to the slip 100 using any means known to one of ordinary skill.

FIG. 5A also shows that the driver 150 comprises an axial passage 155 through which the mandrel 20 extends when the driver 150 is seated thereon. In a preferred embodiment, the mandrel 20 extends through the axial passage 155 of the first, second, third and fourth drivers 41-44. The inner diameter of the axial passage 155 can be substantially the same as the outer diameter of the mandrel 20.

As shown in FIG. 2, movement of one or both of the first and second drivers 41,42 toward each other can angle the first and second pressure arms 35,36 outward to thereby move the first slips 31 outward relative to the mandrel 20. Movement of one or both of the third and fourth drivers 43,44 toward each other can angle the third and fourth pressure arms 37,38 outward to thereby move the second slips 32 outward relative to the mandrel 20. Consequently, as noted above, the first and second slips 31,32 can be moved outward relative to the mandrel 20 to engage the one or more sets of ridges or teeth 102 of the first and second slips 31,32 with an inner surface of a casing or production tubing.

Referring again to FIGS. 1 and 2, the frac plug 10 can comprise a seal 50 positioned between the first slip 31 and the second slip 32. The seal 50 can have a hole aligned with and continuous with the axial passage 151 of the first, second, third and fourth drivers 41-44. Preferably the hole of the seal 50 has an inner diameter that is substantially the same as the outer diameter of the mandrel 20. The mandrel 20 can extend through the hole of the seal 50 so that the seal 50 sits on the mandrel 20, can slide on the mandrel 20, and can rotate on the mandrel 20. The seal 50 can be an elastomeric seal and can be configured to withstand the environment of the wellbore. For example, the seal 50 can be configured to withstand contact with sour gas and high temperatures. The seal 50 can be a single segment seal or preferably can comprise a plurality of segments. For example, the seal 50 can comprise a central seal 51 positioned between two smaller seals, such as a first seal 52 and a second seal 53.

In an embodiment, the first seal 53 can have a bevel, for example a forty degree bevel, which rests on a complementary bevel of a first seal back-up 54. As shown in FIG. 7A, the first seal back-up 54 can be integral with and/or fixedly connected to the second driver 42. The second seal 52 can have a bevel, for example a forty degree bevel, which rests on a complementary bevel of a second seal back-up 55. As shown in FIG. 7B, the second seal back-up 52 can be integral with and/or fixedly connected to the third driver 43. The central seal 51 can have bevels, for example seventy degree bevels, that rest on complementary bevels of the first and second seals 52,53. These bevel angles are non-limiting and illustrative only, and one of ordinary skill will recognize that the specific angles implemented in the frac plug 10 can be adjusted based on the parameters of the operation, such as wellbore size, and proportionality to other components of the frac plug 10.

The first and second seal back-ups 54,55 can sit on the mandrel 20, can slide on the mandrel 20, and can rotate on the mandrel 20. The first and second seal back-ups 54,55 preferably have an inner diameter that is substantially the same as the outer diameter of the mandrel 20. The first and second seal back-ups 54,55 preferably have an outer diameter that is substantially the same relative to each other and the first, second, third and fourth drivers 41-44.

Preferably one or more of the mandrel 20, the first driver 41, the first pressure arms 35, the first slips 31, the second pressure arms 36, the second driver 42, the first seal back-up 54, the second seal back-up 55, the third driver 43, the third pressure arms 37, the second slips 32, the fourth pressure arms 38, the fourth driver 44 and the crown 24 (collectively hereafter “the components”) comprise a decomposable non-metallic material, such as a composite material. “Decomposable” means that the material is stable at the time of use and then is separated into smaller pieces by chemical and/or thermal conditions. Preferably the pieces formed by decomposition can be washed to surface by directing fluid through the wellbore.

For example, one or more of the components can comprise a decomposable resin, such as a fiber e.g. a glass fiber. As another example, one or more of the components can comprise a resin-fiber mixture comprising metallic or non-metallic particulates (e.g. magnesium particulates) which can react with chemicals directed into the wellbore to initiate and/or accelerate decomposition. As yet another example, one or more of the components can comprise a material that is water soluble and/or dissolves in saline water, brine water, or chemicals such as hydrogen chloride or another acid, and such liquids can be directed down the wellbore to the frac plug 10. In this regard, chemicals such as hydrogen chloride can initiate and/or accelerate the decomposition. Additionally or alternatively, decomposition can be initiated and/or accelerated by the temperature in the wellbore, for example a temperature between 150 and 380° F.

In a preferred embodiment, the first and second slips 31,32 comprise a decomposable material that is coated with a thin metal coating that breaks down within one to twenty-four hours after being exposed to the temperature of the wellbore. After the thin metal coating breaks down, at least a portion of the decomposable material previously covered by the coating is exposed, and decomposition of the slip can be initiated and/or accelerated as discussed above.

The frac plug 10 can be positioned and set in the wellbore, for example as discussed hereafter. Coil tubing, wire lines and/or other devices can be used to position the frac plug 10 in the wellbore. For example, a hydraulic setting tool can be used to set the frac plug 10. The hydraulic setting tool can comprise a rod that connects to the mandrel 20, e.g. by inserting into a ring connected to the mandrel 20. In a preferred embodiment, the rod connects to the mandrel 20 by complementary threads. The hydraulic setting tool can comprise a sleeve that can abut the fourth driver 44.

The setting tool can receive a signal from the surface, such as an electric charge, and can respond by pulling the rod upward relative to the sleeve. The pulling of the rod upward also pulls the crown 24 and the mandrel 20 upward into the sleeve. As a result of the sleeve abutting the fourth driver 44, the fourth driver 44 is pushed downward on the mandrel 44. The nose cone 21 is pulled upward with the mandrel 20 and thus pushes the first driver 41 upward.

As shown in FIG. 2, these axial forces move the first and second drivers 41,42 closer to each other such that the first and second pressure arms 35,36 rotate outward relative to the mandrel 20 and extend the first slips 31 outward. The second and third drivers 42,43 are moved closer to each other such that the first and second seal backups 54,55 move closer to each other and force the seal 50 to expand outward. The third and fourth drivers 43,44 are moved closer to each other such that the third and fourth pressure arms 37,38 rotate outward relative to the mandrel 20 and extend the second slips 32 outward.

As a result, the first and second slips 31,32 can be moved outward relative to the mandrel 20 to engage the one or more sets of ridges or teeth 102 with an inner surface of a casing or production tubing. That first and second seal back-ups 54,55 can be moved toward each other to expand the seal 50 into engagement with an inner surface of a casing or production tubing. The complementary threads by which the rod of the setting tool is connected to the mandrel 20 can be configured to shear after the rod has pulled the mandrel 20 upward to the extent necessary to set the frac plug 10. The shearing of the complementary threads can disconnect the rod from the mandrel 20 and allow the setting tool to be pulled upward away from the frac plug 10 and removed from the wellbore.

Then an upper frac plug 10 can be positioned and set in the wellbore in a substantially similar way so that the seals 50 of the two frac plugs 10 isolate a hydrocarbon-bearing zone. The first and second slips 31,32 of the two frac plugs 10 can maintain the positions of the two frac plugs 10 within the wellbore. The isolated hydrocarbon-bearing zone can then be fractured. At least a portion of each of the frac plugs 10 can decompose as discussed above. Any remainder of the frac plugs 10 can be removed from the wellbore by drilling or milling out.

Accordingly, another aspect of the present disclosure is a method for using a frac plug in a wellbore. The method can comprise one or more of: (i) positioning the frac plug in the wellbore at a desired depth, (ii) setting the frac plug, the setting of the frac plug comprising decreasing the axial distance between one of the drivers and an adjacent driver to rotate pressure arms outward to engage the wellbore or a casing in the wellbore with a slip rotatably attached to the pressure arms, (iii) engaging a seal with the wellbore or the casing in the wellbore, and (iv) after at least a portion of the frac plug decomposes, drilling through any remainder of the frac plug.

Step (ii) can comprise using a setting tool to pull a mandrel and/or a nose cone attached thereto upward while maintaining the position of the uppermost driver or while pushing the uppermost driver downward. Step (ii) can comprise decreasing the axial distance between another one of the drivers and an adjacent driver to rotate additional pressure arms outward to engage the wellbore or the casing in the wellbore with an additional slip rotatably attached to the additional pressure arms. Step (iii) can occur at least partially contemporaneously with Step (ii) and can comprise decreasing the axial distance between a seal back-up and an adjacent seal back-up to force the seal to expand. In an embodiment, the seal back-up can be pushed toward the adjacent seal-back-up as a result of the pulling of the mandrel and/or the nose cone attached thereto. For example, the seal back-up can be fixedly attached to and/or integral with one of the drivers, and the adjacent seal back-up can be fixedly attached to and/or integral with another one of the drivers. The decomposition in Step (iv) preferably begins within one to twenty-four hours after the frac plug is introduced into the wellbore and more preferably is completed within one to twenty-four hours after the frac plug is introduced into the wellbore

In yet another aspect of the present disclosure, a decomposable slip 200 is provided as generally illustrated in FIGS. 8A-8F. The decomposable slip 200 can comprise a body 201 comprising a decomposable material, and the decomposable slip 200 can further comprise a coating 202. The decomposable slip 200 can comprise an aperture 203 through which the mandrel of a frac plug can extend, and the coating 202 can cover at least the outer side of the body 201 opposite from the aperture 203. The inner diameter of the body 201 can form the aperture 203.

Preferably at least a portion of the aperture 203 of the decomposable slip 200 has an inner diameter that is substantially the same as the outer diameter of the mandrel on which the decomposable slip 200 is intended for use. In an embodiment, the decomposable slip 200 sits on the mandrel, can slide on the mandrel, and can rotate on the mandrel. Preferably the body 201 has a thickness greater than that of the coating 202. For example, the body 201 can have an outer diameter of about 4.25 inches and can have at least a portion having an inner diameter of about 3.1 inches, and the coating 202 can have a thickness of about 0.05 inches. These dimensions are non-limiting and illustrative only, and one of ordinary skill will recognize that the specific dimensions implemented in the decomposable slip 200 can be adjusted based on the parameters of the operation, such as wellbore size, and proportionality to other components of the frac plug 10.

The coating 202 can comprise a metal material that breaks down within one to twenty-four hours after being exposed to the temperature of the wellbore. After the coating 202 breaks down, the body 201 of decomposable material is exposed. For example, the body 201 can comprise a decomposable resin, such as a fiber e.g. a glass fiber. As another example, the body 201 can comprise a resin-fiber mixture comprising magnesium particulates which can react with chemicals directed into the wellbore to initiate and/or accelerate decomposition. As yet another example, the body 201 can comprise a material that is water soluble and/or dissolves in saline water, brine water, or chemicals such as hydrogen chloride or another acid, and such liquids can be directed down the wellbore to a frac plug comprising the slip 200. In this regard, chemicals such as hydrogen chloride can initiate and/or accelerate the decomposition. Additionally or alternatively, decomposition can be initiated and/or accelerated by the temperature in the wellbore, for example a temperature between 150 and 380° F.

The decomposable slip 200 can have an outer diameter having one or more sets of ridges or teeth 210. The one or more sets of ridges or teeth 210 can be configured to engage an inner diameter of a casing or production tubing when the frac plug is set. Preferably the coating 202 of the decomposable slip 200 comprises the exterior surfaces of the one or more sets of ridges or teeth 210. For example, as shown in FIGS. 8A and 8F, the body 201 of the decomposable slip 200 can be positioned inward relative to the coating 202 in a radial direction. The one or more sets of ridges or teeth 210 can form the outer side of the slip 200 in the radial direction, and the coating 202 can cover some or all of the outer side of the slip 200.

In an embodiment, the decomposable slip 200 can be used on a frac plug comprising a mandrel having a crown on one end and a nose at the other end. Any number of the decomposable slips 200 can be disposed about the mandrel between the crown and the nose. The frac plug can comprise one or more seals disposed between the decomposable slips 200. Each of the one or more seals can be an elastomeric seal.

In an embodiment, a first slip back-up can be positioned on the mandrel, adjacent to the decomposable slip 200 that is adjacent the crown. In addition, a second slip back-up can be positioned on the mandrel, adjacent to the decomposable slip 200 that is adjacent to the nose.

FIGS. 10A-10D show an embodiment of the decomposable slip 200 in which the one or more sets of ridges or teeth 210 comprise buttress-style teeth. Each of the buttress-style teeth can present a flat outer surface generally parallel to the axis of the frac plug on which the decomposable slip 200 is positioned. For each of the buttress-style teeth, one of the sides extending inward from the outer surface can have an angle and/or a length that is different than that of the other side extending inward from the outer surface.

FIGS. 11A-11D show an embodiment of the decomposable slip 200 in which the one or more sets of ridges or teeth 210 comprise acme-style teeth. Each of the acme-style teeth can present a flat outer surface generally parallel to the axis of the frac plug on which the decomposable slip 200 is positioned. For each of the acme-style teeth, the sides extending inward from the outer surface can be generally symmetrical. As shown in these figures, flat base surfaces from which the acme-style teeth extend outward can separate each of the acme-style teeth from the adjacent teeth.

FIGS. 12A-12D show an embodiment of the decomposable slip 200 in which the one or more sets of ridges or teeth 210 comprise parallelogram-style teeth. Each of the parallelogram-style teeth can present a flat outer surface generally parallel to the axis of the frac plug on which the decomposable slip 200 is positioned. For each of the parallelogram-style teeth, the sides extending inward from the outer surface can be generally parallel to each other. As shown in these figures, flat base surfaces from which the parallelogram-style teeth extend outward can separate each of the parallelogram teeth from the adjacent teeth.

FIGS. 13A-13D show an embodiment of the decomposable slip 200 in which the one or more sets of ridges or teeth 210 comprise buttress-style teeth, and the number of the buttress-style teeth is less than that of the embodiment shown in FIGS. 10A-10D.

As generally illustrated in FIGS. 8F, 10B, 10C, 11B, 11C, 12B, 12C, 12B, 12C, 13B and 13C, the decomposable slip 200 can be formed by segments to facilitate the expansion of the decomposable slip. Each segment can be connected to adjacent segments to form a continuous ring before expansion, and then expansion (e.g., under axial pressure) can separate at least a portion of the segment from the adjacent segments. The connections between segments can be any suitable mechanical connection known to the skilled artisan, such as a male-female connection, a non-limiting example of which is the dovetail-type connection shown in the figures. However, the segment connections are not limited to a specific embodiment. Moreover, although each embodiment of the decomposable slip 200 is shown with four segments, the segments are not limited to a specific number thereof.

FIGS. 9A and 9B show an embodiment of a frac plug 300 in which the decomposable slip 200 can be used. The frac plug 300 can comprise a mandrel 305, a crown 307, a load ring 380, a first slip 310, a second slip 312, a first slip back-up 320, a second slip back-up 322, a first anti-extrusion ring 330, a second anti-extrusion ring 332, a seal 340, a nose 350, and a pump-down ring 360. Each of the first slip 310 and the second slip 312 can be the decomposable slip 200.

The first slip back-up 320 can be adjacent to the first slip 310. At least a portion of the first slip back-up 320 can be tapered to at least partially rest within the first slip 310 so that axial force pushing the first slip back-up 320 toward the first slip 310 (such as the axial exerted during setting of the frac plug 300) can expand the first slip 310 into the inner diameter of the casing of the wellbore (as generally shown in FIG. 8F). The second slip back-up 322 can be adjacent the second slip 312. Similarly, at least a portion of the second slip back-up 322 can be tapered to at least partially rest within the second slip 312 so that axial force pushing the second slip back-up 322 toward the second slip 312 (such as the axial force exerted during setting of the frac plug 300) can expand the second slip 312 into the inner diameter of the casing of the wellbore (as generally shown in FIG. 8F).

For example, as shown in FIG. 8B, the decomposable slip 200 (one or both of first and second slips 310,312 in FIG. 9B) can have a bevel 220 on the inner diameter, opposite from the one or more sets of ridges or teeth 210. As shown in FIG. 9B, the bevel of the first slip 310 can be complementary to a bevel of the first slip back-up 320. The bevel of the second slip 312 can be complementary to a bevel of the second slip back-up 322.

Setting the frac plug 300 can move the first slip back-up 320 toward the first slip 310 in an axial direction such that the first slip back-up 320 forces the first slip 310 to expand outward. Similarly, setting the frac plug 300 can move the second slip back-up 322 toward the second slip 312 in an axial direction such that the second slip back-up 322 forces the second slip 312 to expand outward.

The decomposable slip 200 shown in FIGS. 8A-8F that can be one or both of first and second slips 310,312 in FIG. 9B can have reliefs cut therein so that the decomposable slip 200 has a plurality of segments, for example four or five segments. The axial movement of the adjacent slip back-up into and under the decomposable slip 200 can expand each of the segments outward to engage the wellbore or a casing in the wellbore. In an embodiment, the decomposable slip 200 can comprise male connectors, e.g. tongues, and each of the male connectors can extend from a side of a corresponding segment into a female connector, e.g. a hole, in the side of the adjacent segment. The male-female connections can maintain alignment of the segments of the decomposable slip 200 prior to expansion.

The mandrel 305 can have the crown 307 on an upper or first end, and the nose 350 can be disposed about or connected to the mandrel 305 at a lower or second end. The mandrel 305 can be similar to the mandrel 20 discussed previously herein or another mandrel used in downhole operations.

The first anti-extrusion ring 330 can be disposed about the mandrel 305 adjacent the first slip back-up 320. The first anti-extrusion ring 330 can be disposed between the first slip back-up 320 and the seal 340. The second anti-extrusion ring 332 can be disposed about the mandrel 305 adjacent the second slip back up 322. The lower anti-extrusion ring 332 can be disposed between the seal 340 and the second slip back up 322. The seal 340 can be disposed between the anti-extrusion rings 330 and 332. The seal 340 is depicted having three segments, but the seal 340 can include one or more segments.

The load ring 380 can be disposed about the mandrel 305 adjacent or proximate to the crown 307. The load ring 380 can reinforce a portion of the mandrel 305 to enable the mandrel 305 to withstand high pressures.

The pump down ring 360 can be disposed about the nose 350. For example, the pump down ring 360 can be placed within a groove formed into the nose 350. The nose 350 can thread or otherwise connect to the lower or second end of the mandrel 305.

FIGS. 14A, 14B, 15A, 15B, 16A and 16B show the mandrel 305, the load ring 380, and their interaction with the decomposable slip 200 in the frac plug 300 in greater detail. The mandrel 305 is generally illustrated in FIGS. 14A and 14B, the load ring 380 is generally illustrated in FIGS. 15A and 15B, and the interaction of the mandrel 305 and the load ring 380 with the decomposable slip 200 in the frac plug 300 is generally illustrated in FIGS. 16A and 16B.

FIGS. 9A, 9B, 16A and 16B and the corresponding disclosure above are merely directed to non-limiting examples of a frac plug 300 in which the decomposable slip 200 can be used. These examples are non-limiting and illustrative only; the decomposable slip 200 can be used on any frac plug known to one of ordinary skill. For example, the decomposable slip 200 can be used on the frac plug 10 such that the frac plug 10 comprises the first slips 31 and, uphole from the first slips 31, the decomposable slip 200. As another example, the decomposable slip 200 can be used on the frac plug 10 such that the frac plug 10 comprises the second slips 32 and, downhole from the second slips 32, the decomposable slip 200. As yet another example, the slip 100 and the pressure arms 110 can be used on the frac plug 300 such that one of the first and second slips 310,312 comprises the slip 100 and the pressure arms 110 and the other one of the first and second slips 310,312 comprises the decomposable slip 200. In this regard, one of ordinary skill will understand that features of the frac plug 10 and the frac plug 300 can be interchanged.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims. 

The invention is claimed as follows:
 1. A fractionation plug comprising: a first driver; a first pressure arm rotatably connected to the first driver; a second driver; a second pressure arm rotatably connected to the second driver; and a first slip rotatably connected to the first pressure arm and rotatably connected to the second pressure arm.
 2. The fractionation plug of claim 1 further comprising: a third driver; a third pressure arm rotatably connected to the third driver; a fourth driver; a fourth pressure arm rotatably connected to the fourth driver; and a second slip rotatably connected to the third pressure arm and rotatably connected to the fourth pressure arm.
 3. The fractionation plug of claim 2 further comprising: at least one seal; a first seal back-up fixedly connected to and/or integral with the second driver and comprising a bevel complementary to a first portion of the at least one seal; and a second seal back-up fixedly connected to and/or integral with the third driver and comprising a bevel complementary to a second portion of the at least one seal that is at an opposite end of the at least one seal from the first portion.
 4. The fractionation plug of claim 1 wherein the first driver comprises an axial slot into which a portion of the first pressure arm inserts.
 5. The fractionation plug of claim 4 wherein the first driver comprises a socket in which a pin is positioned to extend through the portion of the first pressure arm inserted into the axial slot.
 6. The fractionation plug of claim 1 wherein the first pressure arm, the first slip, and the second pressure arm each comprise an aperture through which a pin is inserted to connect the first pressure arm, the first slip, and the second pressure arm to each other.
 7. A fractionation plug comprising a material formulated to decompose in one to twenty-four hours under typical wellbore conditions.
 8. The fractionation plug of claim 7, having an outside diameter configured such that the fractionation plug can be installed in casing or tubing with an inside diameter from 2 inches to 4 inches.
 9. The fractionation plug of claim 8, configured to be expanded to set in casing or tubing with an inside diameter from 2 inches to 5.5 inches.
 10. The fractionation plug of claim 7, designed to be installed and maintain isolation of hydrocarbon bearing zones for a predetermined period of time.
 11. The fractionation plug of claim 7 wherein the fractionation plug is configured to begin to decompose and release from a wellbore in which the fractionation plug is positioned, when subjected to a chemical selected from the group consisting of water, acid, alkaline and non-alkaline.
 12. The fractionation plug of claim 7 wherein the fractionation plug is configured to undergo decomposition catalyzed by a temperature of a wellbore and/or a fluid in a wellbore.
 13. The fractionation plug of claim 7 wherein the fractionation plug is configured to be installed on at least one of e-line, wireline or coil tubing.
 14. The fractionation plug of claim 7 wherein the fractionation plug is configured to be drilled out with conventional tubing or coiled tubing.
 15. A slip configured to be mounted on a mandrel of a fractionation plug, the slip comprising: a body comprising a decomposable material; and a coating at least partially covering the body, the coating comprising a metal material.
 16. The slip of claim 15, wherein the metal material is formulated to at least partially decompose within one to twenty-four hours after being exposed to a temperature between 150 and 380° F., and the slip is configured such that the at least partial decomposition of the metal material exposes at least a portion of the body that was previously covered by the coating.
 17. The slip of claim 15, comprising teeth comprising exterior surfaces comprising at least a portion of the coating.
 18. The slip of claim 17, wherein the teeth form an outer side of the slip, and the coating completely covers the body on at least the outer side of the slip.
 19. The slip of claim 15, wherein the decomposable material of the body comprises a decomposable resin.
 20. The slip of claim 15, wherein the decomposable material of the body comprises a resin-fiber mixture comprising metallic or non-metallic particulates. 